Exception Handling in php

Jun 20, 2026Trushi Jasani

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Exception handling lets you deal with runtime errors gracefully without crashing your application.

Basic Try-Catch

<?php
try {
    $result = 10 / 0; // This won't throw in php, but the concept applies
    throw new Exception("Something went wrong!");
} catch (Exception $e) {
    echo "Caught: " . $e->getMessage();
}
// Caught: Something went wrong!
?>

---

Exception Methods

The Exception class provides useful methods:

<?php
try {
    throw new Exception("File not found", 404);
} catch (Exception $e) {
    echo $e->getMessage();  // File not found
    echo $e->getCode();     // 404
    echo $e->getFile();     // path to this php file
    echo $e->getLine();     // line number of throw
    echo $e->getTraceAsString(); // stack trace
}
?>

---

Multiple Catch Blocks

Handle different exception types differently:

<?php
function divide($a, $b) {
    if (!is_numeric($a) || !is_numeric($b)) {
        throw new InvalidArgumentException("Arguments must be numbers.");
    }
    if ($b == 0) {
        throw new DivisionByZeroError("Cannot divide by zero.");
    }
    return $a / $b;
}

try {
    echo divide(10, 0);
} catch (InvalidArgumentException $e) {
    echo "Invalid input: " . $e->getMessage();
} catch (DivisionByZeroError $e) {
    echo "Math error: " . $e->getMessage();
} catch (Exception $e) {
    echo "General error: " . $e->getMessage();
}
?>

---

The finally Block

Code in finally always runs, whether an exception occurred or not:

<?php
function readCustomFile($path) {
    $file = fopen($path, "r");

    try {
        if (!$file) throw new Exception("Cannot open file.");
        // process file...
    } catch (Exception $e) {
        echo "Error: " . $e->getMessage();
    } finally {
        if ($file) fclose($file); // always close the file
        echo "File operation complete.";
    }
}
?>

---

Custom Exception Classes

Create meaningful exception types for your application:

<?php
class ValidationException extends Exception {
    private array $errors;

    public function __construct(array $errors, $message = "Validation failed") {
        parent::__construct($message);
        $this->errors = $errors;
    }

    public function getErrors(): array {
        return $this->errors;
    }
}

class NotFoundException extends Exception {
    public function __construct(string $resource, $id) {
        parent::__construct("$resource with ID $id not found.", 404);
    }
}
?>

Using custom exceptions:

<?php
try {
    throw new ValidationException(["name" => "Name is required"]);
} catch (ValidationException $e) {
    foreach ($e->getErrors() as $field => $msg) {
        echo "$field: $msg<br>";
    }
}

try {
    throw new NotFoundException("User", 99);
} catch (NotFoundException $e) {
    echo $e->getMessage();  // User with ID 99 not found.
    echo $e->getCode();     // 404
}
?>

---

Catching Multiple Exception Types (php 8)

<?php
try {
    // code that might throw
} catch (InvalidArgumentException | NotFoundException $e) {
    echo "Caught: " . $e->getMessage();
}
?>

---

Re-throwing Exceptions

<?php
function process() {
    try {
        throw new Exception("Low-level error");
    } catch (Exception $e) {
        // log it, then re-throw with more context
        throw new RuntimeException("Processing failed: " . $e->getMessage(), 0, $e);
    }
}

try {
    process();
} catch (RuntimeException $e) {
    echo $e->getMessage();
    echo "Caused by: " . $e->getPrevious()->getMessage();
}
?>

---

Built-in php Exception Classes

Class	Use Case
Exception	General exceptions
RuntimeException	Runtime errors
InvalidArgumentException	Wrong argument type
LogicException	Programming logic errors
OutOfRangeException	Invalid index or range
DivisionByZeroError	Division by zero
TypeError	Wrong type passed

Best Practice: Always catch the most specific exception types first, then more general ones. Never leave an empty catch block — always log or handle the error meaningfully.